Porphyrin Molecules Research Articles

Effect of the linkage modes of thiolated ethynyl groups on the spin-dependent electronic transport properties in transition metal porphyrin molecular junctions

Using density functional theory and nonequilibrium Green’s function method, the spin-dependent electronic transport properties of six transition metal porphyrin molecules (VP, CrP, MnP, FeP, CoP, and NiP), which are linked to gold electrodes through the thiolated ethynyl groups, are investigated. Two different linkage modes (beta linkage and meso linkage) of the substituted ethynyl groups on the porphyrin macrocycle are considered. The results show that the linkage mode of ethynyl groups plays an important role on the spin transport properties of the molecular junctions and the beta linkage is more favorable for the spin filtering efficiency of current than the meso linkages. The spin-up and spin-down energy levels show the different evolutions which is responsible for the difference of spin filtering efficiency between the two linkage modes. The computational results of total current show that the meso-linked molecular junctions have the better conductive performances than the beta-linked ones which may be caused by the different electronic transport paths.

Controlling Hydrogen-Transfer Rate in Molecules on Graphene by Tunable Molecular Orbital Levels.

Molecular switches are building blocks of potential interest to store binary information, especially when they can be organized in periodic lattices. Among the variety of possible systems, switches based on hydrogen transfer are of special importance because they allow the switching operation to occur without severe conformational change that may interfere with neighboring molecular units. We have studied the excitation process of hydrogen transfer inside porphyrin molecules assembled on a graphene surface, using a low-temperature scanning tunneling microscope. We show that this hydrogen transfer is induced by an electronic resonant tunneling process through the molecular orbitals. Using nitrogen doping of graphene, we tune the rate of hydrogen transfer by shifting the molecular orbital energies owing to the charge transfer at nitrogen dopant sites in the graphene lattice. The control of the switching process allows the storage of information inside a molecular lattice, which is demonstrated by writing an artificial pattern inside a molecular island.

Aggregation-enhanced adsorption and optoelectronic performance of metal-free organic dye on anatase (1 0 1) toward water-splitting purpose: A first-principles investigation

Metal-free organic dye-sensitized water splitting systems have recently been experimentally verified to afford good optoelectronic properties for the water-splitting purpose. In this manuscript, we employ first-principles calculations to understand the aggregation of the metal-free organic dye on TiO2 in a water-splitting photoanode. The calculation suggests that the aggregation stabilizes the adsorption of the water-splitting organic porphyrin molecule on TiO2 and enhances the electronic and optical properties of the water-splitting photoanode. This study facilitates the fundamental understanding of the metal-free organic dye-based water-splitting systems.

Mitochondria‐Targeted Nanoscale MOFs for Improved Photodynamic Therapy

AbstractDue to the existence of hypoxic microenvironment, the efficacy of photodynamic therapy (PDT) is frequently weakened. As a result, targeted treatment toward oxygen‐rich mitochondria is considered as a promising cancer therapy. Herein, both triphenylphosphine (TPP) and folic acid (FA) are simultaneously grafted onto nanoscale metal‐organic frameworks (NMOFs) to realize dual‐targeting delivery of the nanoplatforms into cancer cells and their mitochondria via the proposed phosphorylation modification strategy. A large amount of highly efficient photosensitizer of porphyrinic molecules is integrated into the NMOFs with a uniform particle size of about 65 nm. Thanks to the strong Zr−O−P bonding, a dense coverage of phosphonate‐conjugating targeting molecules on NMOFs is obtained and each surficial unsaturated Zr−O cluster is adequately occupied. The resultant dual‐targeting NMOFs feature high biostability and biocompatibility, as well as improved cellular uptake and mitochondrial accumulation. The PDT efficacy of these dual‐targeting NMOFs is significantly improved with a low IC50 of 0.74 μM upon 10 min light radiation, which is at least four times higher than that of non‐targeting counterparts. This phosphorylation strategy would be hopeful for immobilizing a variety of biogenic groups on NMOFs to make them targetable to various specific organelles and to improve the therapy efficacy on related diseases.

Surface photochemical studies of nano-hybrids of A3B porphyrins and Fe3O4 silica-coated nanoparticles

This study reports a surface photochemistry behaviour of two tetrapyrrolic structures: 5,10,15,20-tetra-(4-carboxymethylphenyl) porphyrin (P1.1) and 5-(4-hydroxy-3-methoxyphenyl)-10,15,20-tris-(4-carboxymethylphenyl) porphyrin (P1.2), covalently bound to silica-coated magnetite nanoparticles (Fe3O4@SiO2) imbibed into a polyethylene glycol (PEG) matrix and in the form of a fine powder. The initial compounds and the nano-hybrids imbibed in the PEG matrix were characterized using Fourier transformed infrared spectroscopy (FT-IR), diffuse reflectance absorption spectroscopy for ground state molecules (GSDR), X-ray diffaction (XRD), transmission electron electron microscopy (TEM) as well as several luminescence emission spectroscopies. The combined use of these methodologies enabled us to obtain a surface photochemistry characterization of these new nano-hybrid materials.For the powdered samples of P1.1 or P1.2 and Fe3O4@SiO2 imbibed into the powdered PEG a detailed absorption study and a correlation of fluorescence emission intensity with the magnetite concentration were performed. New covalent bonds porphyrin-Fe3O4@SiO2 were detected using FT-IR transmission spectra. A donor-acceptor interaction with change of the oxidation level of the porphyrins was also observed. Fluorescence emission quantum yields and lifetimes of the two porphyrins were determined for all samples and two populations of the porphyrin molecules exist, free porphyrin (unquenched) and porphyrin with Fe3O4@SiO2 NPs attached, the quenched porphyrin. In this way, the amount of the available excited porphyrin for singlet oxygen formation is reduced, therefore the presence of the Fe3O4@SiO2 NPs may not favor this specific PDT action by the Type II mechanism, but it prevents aggregation of the porphyrins, even when a PEG matrix is used, and Type I mechanisms remain active.

63P - Study of photodynamic therapy in vitro

BackgroundPhotosensitizers (PS) are commonly used in photodynamic therapy to treat skin cancer. PS molecules bind to cell membrane and damage it by singlet oxygen (SO) generated under illumination. In our laboratory, we study in vitro the processes involved in photodynamic therapy on a model bilayer lipid membranes (BLM) by measuring the boundary potential applying the Intramembrane Field Compensation Method (Sokolov and Kuz’min, Biofizika, 25:170, 1980). MethodsThis method allowed to monitor the binding of PS on BLM and damage of target molecules (TM) of SO - di-4-ANEPPS under excitation of PS by light. In present investigation, we studied the adsorption and photodynamic efficiency of new positively charged porphyrins, namely b-imidazolyl substituted porphyrin and it’s Zn(II) and In(III) complexes; and two phosphorus (V) complexes of meso-(p-pyridyl)-triphenylporphyrin bearing hydroxyl and ethoxyl axial ligands. We observed a linear dependence of the boundary potential change on the logarithm of concentrations of each PS. ResultsThe photodynamic efficiency of these porphyrins was assessed by determining the rate of oxidation (R) of TM adsorbed either on the same or opposite surface of the BLM where molecules PS were present. The values R for both positions of TM were close indicating that BLM is highly permeable to singlet oxygen. The values R were proportional to surface density of the porphyrin molecules in the membrane. ConclusionsThis investigation indicate that the main factor influencing the photodynamic efficiency of the porphyrins is their adsorption on the BLM. The work was supported by the Russian Foundation for Basic Research (project 19-04-00694) and the Ministry of Education and Science of the Russian Federation in the framework of Increase Competitiveness Program of NUST «MISiS» (№ К4-2017-053). Legal entity responsible for the studyNational University of Science and Technology. FundingNUST-MISiS, Russian Science Foundation, Russian Academy of Sciences. DisclosureAll authors have declared no conflicts of interest.

Preparation and aggregate state regulation of co-assembly graphene oxide-porphyrin composite Langmuir films via surface-modified graphene oxide sheets

Constructing graphene oxide (GO)-based 2D nanomaterials via facile and appropriate methods have aroused much attention due to their potential applications in many fields. Herein, by Langmuir-Blodgett (LB) technique, we have successfully fabricated GO-based films composited with porphyrin molecules. By the reaction of diazotization and Fischer osazone, different surface states of GO sheets with sulfonate groups were obtained. The amphiphilic GO and surface modified GO sheets could spontaneously form composite films at the air/water interface with porphyrin molecules (TMPyP) by electrostatic interactions and π-π stacking. Since the sheets can perfectly float on the interface, the TMPyP molecules were adsorbed on the floating-layers and self-assembled into highly ordered J-aggregate structures. The morphological characterization results showed the composite films with smooth and dense surface. Due to the different surface state of the nanosheets, the aggregate states of porphyrin molecules were different which could be demonstrated in the UV–vis spectra. The results indicated that the induction of sulfonate groups and the types of oxygen-containing groups have played important roles for regulating the aggregate state of porphyrin molecules.

Copper (II) complexes modified with water-soluble porphyrin and various small molecules ligand for DNA binding and potential selectivity antitumor agents

Many strategies have been used in treatment of cancer, but currently the chemotherapy is still the main force, unfortunately, general agents exhibit inevitable toxicity and inferior selectivity. Therefore, less toxic and high selectivity anticancer reagents have been extensively sought and developed. Here we report a series of Copper (II) complexes CuP1~CuP5 which have good biological activities. Due to the influence of the molecular size, CuP1 displayed the strongest bound with ct-DNA. All of the complexes show positive anticancer activities toward A549, H1975, HepG2 and T47D cancer cells. Additionally, flow cytometry experiments indicated that complexe CuP2 arrest cell cycles at S and G2 phase and mitochondrial membrane potential tests were also performed to explore the mechanism of action. Our findings disclosed that this type of complex represents a potent platform for development of metal anticancer drugs.

Polyethersulfone Mats Functionalized with Porphyrin for Removal of Para-nitroaniline from Aqueous Solution.

The dispersion of para-nitroaniline (p-NA) in water poses a threat to the environment and human health. Therefore, the development of functional adsorbents to remove this harmful compound is crucial to the implementation of wastewater purification strategies, and electrospun mats represent a versatile and cost-effective class of materials that are useful for this application. In the present study, we tested the ability of some polyethersulfone (PES) nanofibers containing adsorbed porphyrin molecules to remove p-NA from water. The functional mats in this study were obtained by two different approaches based on fiber impregnation or doping. In particular, meso-tetraphenyl porphyrin (H2TPP) or zinc(II) meso-tetraphenyl porphyrin (ZnTPP) were immobilized on the surface of PES fiber mats by dip-coating or added to the PES electrospun solution to obtain porphyrin-doped PES mats. The presence of porphyrins on the fiber surfaces was confirmed by UV–Vis spectroscopy, fluorescence measurements, and XPS analysis. p-NA removal from water solutions was spectrophotometrically detected and evaluated.

Renal-clearable ultrasmall covalent organic framework nanodots as photodynamic agents for effective cancer therapy

Covalent organic frameworks (COFs) and their derivatives represent an emerging class of crystalline porous materials with broad potential applications. However, the biomedical applications of them were limited by the large size, low dispersivity, poor bioavailability within cells and metabolic problems. Herein, renal-clearable ultrasmall COF nanodots have been synthesized and utilized as efficient cancer therapy agents. A simple liquid exfoliation strategy was used to prepare COF nanodots. After polyethylene glycol (PEG) conjugation, the PEG coated COF nanodots (COF nanodots-PEG) showed improved physiological stability and biocompatibility. In addition, the well isolated porphyrin molecules endowed COF nanodots-PEG good light-triggered reactive oxygen species production ability, which showed excellent photodynamic therapy efficiency with good tumor accumulation ability. In particular, due to the ultrasmall size, COF nanodots-PEG could be cleared from the body through the renal filtration with no appreciable in vivo toxicity. Our study highlights the potential of COFs-based nanoparticles for biomedical applications.

Binding mode of a cationic porphyrin to parallel and antiparallel thrombin binding aptamer G-quadruplex

The spectral properties of meso-tetrakis (N-methylpyridinium-4-yl)porphyrin (TMPyP) in the presence of parallel and antiparallel G-quadruplexes formed from a thrombin-binding aptamer G-quadruplex (5′-G3T2G3TGTG3T2G3) were investigated in this study. Red shift and hypochromism in the Soret absorption band of TMPyP were observed after binding to both parallel and antiparallel G-quadruplexes. The extent of changes in the absorption spectra were similar for both conformers. No circular dichroism spectrum was induced in the Soret region for both parallel and antiparallel G-quadruplexes. This is suggest that there is no or very weak interaction between electric transitions of nucleobases and porphyrin molecule. The accessibility of the neutral quencher I2 to the G-quadruplex-bound TMPyP was similar for both parallel and antiparallel G-quadruplexes. All these observations suggest that TMPyP was bound at the outside of the quadruplexes, and conceivably interacted with the phosphate group via a weak electrostatic interaction.Communicated by Ramaswamy H. Sarma

Uniaxial Alignment of a Monolayer of Flat-on Free-Base Porphyrins on an Exfoliable Insulating Substrate.

Porphyrins are an extremely valuable class of molecules engaged in a variety of roles spanning from biology to optoelectronics. Manipulation of the chemical and physical properties of the inner cavity of porphyrins has been recognized as crucial for the exploitation of these systems in organic devices, particularly when porphyrins self-organize at the interface with a flat-on orientation of the macrocycle. Such an orientation has been mostly observed on metallic surfaces. Unfortunately, the physical-chemical properties of the molecules result in being largely perturbed due to the molecule-metal interaction. In addition, conducting substrates are unsuited to exploit electrically driven devices based onorganic layers. To overcome these issues, we performed a topology-based analysis of insulating organic single crystal structures to identify a surface which (i) ensures easy exfoliation through mechanical methods, (ii) ensures epitaxial match with an overlayer of close-packed flat-on porphyrin molecules, and (iii) displays chirality. The outcome of this work is represented by a unique crystal of mixed 2,5-diketopiperazine and fumaric acid in a 1:1 ratio. We demonstrate that the (110) surface of this crystal fulfills the aforementioned requirements and, thanks to its peculiar subnanometric corrugations, allows one to grow uniaxially aligned monolayers of flat-on porphyrin molecules assembled through van der Waals interactions.

Adsorption geometry of carboxylic acid functionalized porphyrin molecules on TiO2(110)

Controlling the adsorption geometry of porphyrin molecules on titania surfaces is an important step in the rational design of molecular devices such as dye-sensitized solar cells. We employed X-ray Photoelectron Spectroscopy (XPS) and Near-Edge X-Ray-Absorption Fine Structure (NEXAFS) spectroscopy to determine the binding mode, the electronic structure and the adsorption geometry of carboxylic acid functionalized tetraphenylporphyrin molecules. Molecules with one (mono), two (cis and trans) and four (tetra) carboxylic acid anchoring groups were adsorbed on rutile TiO2(110). XPS shows that the iminic nitrogen atoms at the macrocycle center are partially protonated after adsorption, and that the degree of protonation increases with the number of –COOH functional groups in the molecule. NEXAFS measurements show that molecules with either one or two groups in cis configuration adsorb with the macrocycle tilted away from the surface. In contrast, molecules with two carboxylic-acid groups in trans configuration adsorb with what is probably a flat-lying, but distorted macrocycle. Finally, molecules with four carboxylic-acid groups show no linear dichroism, indicating an intermediate adsorption angle. Our results show how the number and position of the –COOH functional groups determine the molecular adsorption geometry.

Enhanced third order optical nonlinearity in ultrathin amorphous film of tetraphenyl-porphyrin in picosecond regime

The third order optical nonlinearity of ultrathin 5, 10, 15, 20-Tetraphenyl-21H, 23H-porphine (TPP) films fabricated on an ultrasonically cleaned glass-substrate, by high vacuum thermal evaporation method is investigated. The powder X-ray diffraction (XRD) pattern demonstrates the amorphous nature of the fabricated thin film. The atomic force microscopy (AFM) and the field emission scanning electron microscope (FESEM) images show that the surface morphology of thin film composes of randomly oriented particles with the mean surface roughness of 17.73 nm. The structure of TPP thin film portrays a characteristic UV–Visible spectrum due to π-π* transitions in the porphyrin molecule. The photoluminescence spectroscopic study reveals that the TPP exhibits excellent fluorescence emission from S1 singlet excited state. The third order optical nonlinearity is studied using single beam Z-scan technique at 532 nm with picosecond pulsed (Δτ = 30 ps) laser. The TPP thin film exhibits saturation absorption property, with the effective two-photon absorption coefficient (βeff) of the order of 10−6 m/W. The observed nonlinear saturation absorption behavior is largely influenced by one-photon absorption due to the filling effect of the surface states and the localized defect states in the thin film. The closed aperture Z-scan study highlights the self-defocusing nature of the TPP thin film with negative nonlinear refractive index (n2) of the order of 10−13 m2/W. The enhanced n2 value is attributed to the highly polarizable structure of free base TPP molecule and modified electronic band structure due to the strong intermolecular interactions observed in the condensed state.

Tailored porphyrin–gold nanoparticles for biomedical applications

In this review we present an updated survey of the main synthesis methods of gold nanoparticles (AuNPs) in order to obtain various tailored nanosystems for biomedical imaging. The synthesis approach significantly impacts on the AuNPs properties such as surface chemistry, biocompatibility and cytotoxicity. In recent years, nanomedicine emphasized the development of functionalized AuNPs for biomedical imaging. AuNPs are a good option for used as delivery photosensitizer agents for PDT of cancer. For example, the complex formed from AuNPs functionalized with PEGylate porphyrins presents several advantages in the medical field such as a better use in photodynamic therapy because of high triplet states and singlet oxygen quantum yield efficiency of porphyrin molecules.

Solvation interactions and photostability of tetrakis(1-methylpyridyl)porphyrin derivatives

In this paper, a series of water-soluble meso-tetrakis(1′-methyl-pyrid-4- and -3-yl)porphyrin tetratosylate and meso-tetrakis(1′-methyl-pyrid-4- and -3-yl)porphyrin tetraiodide were synthesized with high yields. All synthesized compounds were characterized by 1Н NMR, FT-IR, UV–vis spectroscopy and elemental analysis. The enthalpy changes of meso-tetrakis(1′-methyl-pyrid-4- and 3-yl)porphyrin tetratosylates dissolution in water, alcohol and phosphate buffer (pH = 6.86) were determined by the calorimetric method at 298.15 K. The effect of peripheral substituents and anion of the porphyrin molecule on the enthalpy of solvation have been studied by calorimetry and UV–vis spectroscopy.To understand more clearly the nature of changes in the meso-substituents and anion of a porphyrin molecule, we have also synthesized N-methyl-pyridinium salts (1-methyl-pyridium tosylate and 1-methyl-pyridium iodide) model. The processes of their dissolution under the same solution conditions have been investigated. The nature of the anion and isomerism of the pyridylporphyrin substituent significantly affects the thermochemical characteristics of the compounds transition into solution. In particular, porphyrin-tosylates were found to be solvated several times better than its iodide analogs.Stability to photooxidative degradation is one of the key characteristics of chromophore and characterizes the kinetic stability of a compound in solution under UV-irradiation influence in atmospheric oxygen conditions. In this regard, the stability to photooxidative destruction of porphyrinic salt derivatives has been also measured in aqueous solutions. The results indicated that N-methyl-pyridylporphyrins were stable and slowly degrade under the influence of light radiation in aqueous solutions. It follows from the observed rate constant values of porphyrins (kobs) photooxidative destruction that 4N-substituted porphyrins are much more stable than their 3N-substituted analogs. A similar dependence was observed for the half-flow time of the studied compounds.

Target-induced elimination of photosensitizer and formation insulation layer enabling ultrasensitive photoelectrochemical detection of ochratoxin A

An efficient photoelectrochemical aptasensor with triple signal amplification was developed for sensitive determination of ochratoxin A (OTA). Briefly, gold nanoparticles were decorated onto the GO-CdS-MoS2 nanocomposites to form GO-CdS-MoS2-AuNPs nanostructure, which was utilized as the photoelectrochemical matrix to immobilize the auxiliary DNA (aDNA) for the following hybridization with the complementary OTA aptamer (OTA Apt). Then, porphyrin (TMPyP) molecules employed as an efficient photosensitizer can be intercalated into double-stranded DNA (dsDNA). Thus, an enhanced initial PEC signal was acquired. Upon introduction of OTA, the aptamer-OTA complex was formed and detached from the electrode, while the TMPyP molecules releasing from the platform. The photocurrent signal was highly decreased ascribed to the target induced elimination of photosensitizer. Then, the SiO2@helpDNA (SiO2@hDNA) can be assembled on the electrode through the re-exposed aDNA. Notably, the steric hindrance of the SiO2 and hDNA may effectively depress the electron transfer, thus obviously enlarge the decrement of the photocurrent responses. Under optimized condition, the program shows satisfied analytical performance for OTA with a low detection limit of 0.00021 ng mL−1. Meanwhile, it also presents outstanding reproducibility, stability and specificity. Importantly, the sensing platform provides a new ideal for detection of toxins.

Site-dependent TERS study of a porphyrin molecule on Ag(100) at 7 K

Single-molecule tip-enhanced Raman spectroscopy (TERS) has emerged as an important technique for structural analysis at sub-molecular scale. Here in this work, we report a TERS study of an isolated free-base porphyrin molecule adsorbed on the Ag(100) surface at cryogenic temperature (~7 K). Site-dependent TERS spectra reveal distinct local vibrational information for the chemical constituents within a single molecule. Moreover, distinct spatial features among different Raman peaks can be resolved from the TERS mapping images. These images are found to associate with related vibrational modes, enabling to resolve the mode associated with N–H bonds at the sub-nanometer level. This study will provide deep insights into the symmetry of adsorption configurations and local vibrational information within a single molecule.

Crystal structure of 210,220-bis-(2,6-di-chloro-phen-yl)-4,7,12,15-tetra-oxa-2(5,15)-nickel(II)porpyhrina-1,3(1,2)-dibenzena-cyclo-hepta-deca-phane-9-yne di-chloro-methane monosolvate.

The asymmetric unit of the title compound, [Ni(C52H34Cl4N4O4)]·CH2Cl2, consists of two discrete complexes, which show significant differences in the conformation of the side chain. Each NiII cation is coordinated by four nitro-gen atoms of a porphyrin mol-ecule within a square-planar coordination environment. Weak intra-molecular C-H⋯Cl and C-H⋯O inter-actions stabilize the mol-ecular conformation. In the crystal structure, discrete complexes are linked by C-H⋯Cl hydrogen-bonding inter-actions. In addition, the two unique di-chloro-methane solvate mol-ecules (one being disordered) are hydrogen-bonded to the Cl atoms of the chloro-phenyl groups of the porphyrin mol-ecules, thus stabilizing the three-dimensional arrangement. The crystal exhibits pseudo-ortho-rhom-bic metrics, but structure refinements clearly show that the crystal system is monoclinic and that the crystal is twinned by pseudo-merohedry.

Modifying the Magnetic Anisotropy of an Iron Porphyrin Molecule by an on-Surface Ring-Closure Reaction

The magnetic properties of adsorbed metalloporphyrin molecules can be altered or tuned by the substrate, additional axial ligands, or changes to the molecules’ macrocycle. These modifications influence the electronic configuration of the fourfold-coordinated central metal ion that is responsible for the metalloporphyrins’ magnetic properties. We report a substantial increase in the effective spin moment obtained from sum-rule analysis of X-ray magnetic circular dichroism for an iron metalloporphyrin molecule on Au(111) through its conversion from iron(II)-octaethylporphyrin to iron(II)-tetrabenzoporphyrin in a surface-assisted ring-closure ligand reaction. Density functional theory calculations with additional strong Coulomb correlation (DFT+U) show that the on-surface reaction alters the conformation of the molecule, increasing its planarity and the ion–surface distance. A spin-Hamiltonian fit of the magnetization as a function of field reveals a substantial increase in the intra-atomic magnetic dipole term (Tz) and a decrease in the magnitude of the easy-plane anisotropy upon ring closure. This consequence of the ring closure demonstrates how new magnetic properties can be obtained from on-surface reactions, resulting here in significant modifications to the magnetic anisotropy of the Fe ion, and sheds light onto the molecule–substrate interaction in these systems.